In the electrowinning of a metal, a plurality of cathode plates and anode plates are altenately arranged at equal intervals. Hitherto, cathode plates and anode plates have been hung in an electrolytic cell separately plate by plate, and use of an electrode unit consisting of assembled anode plates and cathode plates has not been known. The reason is that cathodes are used as mother plates on which an electrolyzed metal is deposited and recovered, while anode plates are merely used as electrodes, and it suffices if only cathode plates are taken out of the cell in order to recover the deposited metal.
When the cathode plates and anode plates are separately hung plate by plate in an electrolytic cell as has been done, the electrode plates are liable to swing and often contact each other, thereby causing electrical short circuiting. Therefore, a cathode and an anode are spaced apart at a considerably wide distance in comparison with the thickness of the metal to be deposited on the cathode surface. This makes the electrolytic cell larger and increases electric resistance, which invites inefficiency in electrolysis and increase in power consumption.
Of course, many attempts have been made in order to shorten the distance between the adjacent anode and cathode preventing short-circuiting. For example, rods of an insulating material have been placed in parallel at the bottom of the electrolytic cell, and the lower ends of the electrode plates have been inserted in the spaces between the rods in order to prevent swinging and contacting of the electrodes. However, it is not easy to insert the lower ends of the hanging electrode plates in the spaces between the rods, and even still the short-circuiting is not always perfectly prevented. This is because insertion of the electrode plates is not easy if the insulating rods are long enough, and the electrode plates tend to contact each other at end portions if the insulating rods are short. The anode plates are made of rather soft lead or lead alloy and, therefore, easily bend, which also may cause mutual contacting of electrodes at the edge portions although the central portions are separated. Also there is a danger that anode plates may be bent when they are inserted into the spaces between the insulating rods and cause contacting with the adjacent plate.
It is also known to provide the anode plates with insulating protrusions at the surface thereof to prevent contact with the cathode plates on which the object metal has been deposited. However, it is troublesome to produce anode plates provided with such protrusions, and even such anode plates cannot be stably set in the cell, nor are they free from bending. Thus, they are not practical.
In the conventional electrowinning of a metal, it is rather troublesome to remove only the cathode plates and return them to the cell after stripping the deposited metal. The cathode plates from which the deposited metal has been stripped off are to be inserted again each between the two adjacent anode plates in the electrolytic cell. The operators have to watch the suspended cathode plates and carefully adjust the positions of each cathode plate before they are actually inserted between the anode plates. This requires a considerably long time of operation even for experienced operators.
In the conventional electrowinning of a metal, there is also a problem in the treatment of the electrodes after the electrolysis. In the electrowinning of zinc, which is a typical example of electrowinning, the cathode plates are taken out from the electrolytic cell for stripping of deposited zinc every time one period operation of electrolysis is finished, and again they are immersed in the cell after they have undergone the stripping and other treatments. On the other hand, the anode plates are taken out of the cell after every several cycles of electrolysis for servicing, such as removal of crusts formed on the surface thereof. The crust formed on the anode surface increases the electrolysis resistance and deteriorates electrolysis efficiency. Therefore, it is desirable to remove the crust as frequently as possible. Hitherto, the treatment of the anode plates have been effected once per several times of cathode strippings. The reason is that the cathodes and the anodes are respectively hung plate by plate, and, therefore, it is troublesome to take out the alternately arranged and individually suspended cathodes and anodes separately and to return the two kinds of electrodes respectively to the original positions every time, which increases burden in operation.